1. Field of the Invention
The present invention relates to a fan motor drive device preferably for use, for example, blowing air through a duct.
2. Description of the Related Art
Conventionally, an air blower device is widely used in different fields. For example, in a ceiling-embedded ventilation device, an indoor air is ventilated through a duct by a blower. In such a ventilation device, the load of an air blower device is changed due to the contamination of a duct, the contamination of a filter provided within the duct, etc. International Publication Nos. WO2007/040180 and WO 2009/110219 disclose a configuration in which the fluctuation of a flow rate (wind volume) attributable to the change of a load is reduced by calculating a wind volume from a motor rotation speed and a drive current and controlling the drive of a motor. Furthermore, Japanese Patent Application Publication No. 2008-43083 discloses a configuration in which a motor is driven while detecting the rotational position of a rotor from a drive current without having to separately provide a sensor for detecting the rotational position of the rotor (in a so-called sensor-less manner).
With respect to the control of a motor of such an air blower device, Japanese Patent No. 3653670 discloses a configuration in which a motor is controlled by virtue of so-called vector control.
In a motor, there is a drawback in that the generated torque is changed due to the variation in a rotor magnetic flux intensity at different points of the rotor and further that the rotor magnetic flux intensity varies from motor to motor. As a result, for example, in an air blower device, there is a problem in that the wind volume is changed on a motor-by-motor basis and further that the error of a preset wind volume between motors grows larger.